Identification of multi-dimensional elastic and dissipative properties of elastomeric vibration isolators

Experimental methods must be adopted to characterize the dynamic properties of elastomeric isolators, especially their multi-dimension elastic and dissipative properties. To facilitate a tractable problem statement a rigid body isolation system (under a weight-type preload) is proposed and reduced to a planar problem with 3 degrees of freedom that can be replicated in any vertical plane. First, this article employs modal methods in tandem with analytical, lumped-parameter models to experimentally characterize the dynamic stiffness matrix, including off-diagonal terms. Fundamental stiffness properties are identified about the elastic center, facilitating a clear relationship between component- and system-level dynamics. Dissipative properties are analyzed in terms of global, structural type and mode-dependent viscous type damping formulations. Modal decomposition is employed to demonstrate the effectiveness of the dissipative models for both coupled and uncoupled motions. The proposed characterization method is validated by comparing predicted dynamic properties of a multi-isolator system with measured responses in multiple directions. Finally, physical insight into the underlying behavior of elastomeric interfacial elements is sought by highlighting the role of the elastic center, comparing structural loss factor and viscous damping matrix models, identifying the correlation between surface hardness and Young's Modulus, and briefly comparing non-resonant and resonant methods. Several annular or cylindrical elastomeric devices with varying size and material demonstrate the proposed method's breadth of application; subsequently, two production mounts are utilized for validation purposes. Various identification issues such as uniqueness of the identified stiffness, damping and elastic center properties are discussed throughout the article.